According to dictionary.com, the ASMR definition is:
"Autonomous sensory meridian response (ASMR) is a calming, pleasurable feeling often accompanied by a tingling sensation. This tingle is said to originate in a person's head and spread to the spine (and sometimes the limbs) in response to stimulation. The stimuli that trigger ASMR vary from person to person"
Basically, they're sounds that give you the chills.
Some people love them, and find them relaxing.
Others just find them creepy and disturbing.
I'll let this video from the New Yorker explain it, and why it's so popular. You really need to hear the sounds to know what ASMR eating is.
As it's only quite new, scientifically speaking, there isn't a lot of evidence behind why it works.
John Cline Ph.D has some explanation in his article on PychologyToday.com (full article here: https://www.psychologytoday.com/au/blog/sleepless-in-america/201809/what-is-asmr-and-why-are-people-watching-these-videos).
In a set of studies conducted by Poerio, Blakey, Hostler, & Veltri, (2018) it was found that watching ASMR videos increased positive emotional states only in people who experience ASMR. They also found that ASMR was reliably associated with physiological markers including reduced heart rate and increased skin conductance. These studies used a number of stimuli including videos with male and female voices, videos with sound but no speaking, and non-ASMR videos so that a wide range of stimuli could be investigated. They found that people who experienced ASMR specifically had responses such as tingling and increased calmness only to the ASMR videos and not to control videos. The ASMR responders showed significantly decreased heart rate and significantly increased skin conductance in response to the ASMR videos as compared to the non-ASMR videos.
This is, of course, an emotionally complex response to this type of stimulation in that there was decreased physiological activation as evidenced by the decreased heart rate simultaneous with increased activation or excitement shown by the increased skin conductance measured. This could explain some of the complexity of the experience in which there is relaxation (decreased tension) along with the sensation of excitement (the tingles).
So there's still a lot to work out before it can be used clinically. For now, if it helps, that's great. We can find out why later.
If you've used it to relax, we'd love to hear from you in the comments below.
And if you think it's gross, we want to hear too.